王锐, 张东亮, 张程程, 林青华, 罗明馨, 郑显通, 祝连庆. 中红外量子级联激光器1×16锁相阵列设计[J]. 红外与激光工程, 2024, 53(5): 20240014. DOI: 10.3788/IRLA20240014
引用本文: 王锐, 张东亮, 张程程, 林青华, 罗明馨, 郑显通, 祝连庆. 中红外量子级联激光器1×16锁相阵列设计[J]. 红外与激光工程, 2024, 53(5): 20240014. DOI: 10.3788/IRLA20240014
Wang Rui, Zhang Dongliang, Zhang Chengcheng, Lin Qinghua, Luo Mingxin, Zheng Xiantong, Zhu Lianqing. Design of 1×16 phase-locked array of quantum cascade laser in mid-infrared band[J]. Infrared and Laser Engineering, 2024, 53(5): 20240014. DOI: 10.3788/IRLA20240014
Citation: Wang Rui, Zhang Dongliang, Zhang Chengcheng, Lin Qinghua, Luo Mingxin, Zheng Xiantong, Zhu Lianqing. Design of 1×16 phase-locked array of quantum cascade laser in mid-infrared band[J]. Infrared and Laser Engineering, 2024, 53(5): 20240014. DOI: 10.3788/IRLA20240014

中红外量子级联激光器1×16锁相阵列设计

Design of 1×16 phase-locked array of quantum cascade laser in mid-infrared band

  • 摘要: 针对中红外波段单管量子级联激光器存在输出功率有限的问题,提出相干阵列通过光放大后合束提升激光器功率的方法,研究波长为4.6 μm的1×16量子级联激光器锁相阵列的结构设计与优化。通过设计低传输损耗、高光限制因子的单模波导确定器件各层材料外延厚度;通过设计由100%反射率和50%反射率的布拉格反射镜组成的种子激光器实现4.6 μm单波长激光输出;通过设计由1×2多模干涉耦合器(MMI)和弯曲波导组成的1×16分束器实现低损耗均匀分束并锁相;通过设计输出端口的Al2O3增透膜厚度并利用电注入放大的方式实现激光器阵列的大功率输出。最终确定波导上GaInAs层厚度为0.25 μm,下GaInAs层厚度为0.1 μm,上包层InP厚度为3 μm,下包层InP厚度为1 μm。当单模波导宽度为5 μm时,波导损耗为0.055 dB·cm-1,光限制因子为0.733。100%反射镜刻蚀深度为0.2 μm,周期为728 nm,占空比为0.5,周期数为1000;50%反射镜刻蚀深度为0.2 μm,周期为727 nm,占空比为0.1,周期数为690;当阵列间距为35 μm时,分束器尺寸为3080 μm×605 μm,损耗为0.254 dB,其中MMI尺寸为19 μm×126 μm;出射端口采用0.7 μm的Al2O3增透膜,透射率达到0.975。最后比较了不同放大器阵列间距的温度与远场分布,相关研究结论可为量子级联激光器锁相阵列的研制提供设计参考。

     

    Abstract:
      Objective  Quantum cascade laser (QCL) in the mid-infrared (MIR) band suffer from the problem of limited output power, and many important applications require high power outputs above the watt level and high beam quality. Simply increasing the width of the active region can obtain higher power output, but it often directly affects the beam quality and generates a large amount of heat in the core region that cannot be exported, resulting in the device not being able to operate continuously. If a set of narrow-ridge QCL phase-locked arrays, can greatly improve the thermal efficiency, but also avoid the different phases between the units QCL brought about by the problem of poor beam quality, to facilitate the realization of high-power continuous output.
      Methods  The seed laser is designed with a resonator composed of a 50% Bragg mirror on the front and a 100% Bragg mirror on the back. A stable laser beam with a central wavelength of 4.6 μm is achieved; a thermal simulation analysis was established to determine the array distance at the amplified end; in order to avoid the problem of poor beam quality caused by phase inconsistency between the laser array elements, the 1×16 beam splitter consisting of a multimode interference coupler (MMI) and a bend waveguide is designed, so that the seed optical passing through the beam splitter can maintain the phase consistency and realize the function of uniform beam splitting; Al2O3 anti-reflection coating is plated on the array output port, and optical amplification is completed through the end amplification part to achieve coherent beam enhancement of laser output power.
      Results and Discussions  The simulation results show that the reflectivity of the total and semi-reflector mirrors is 100% and 50% for the beam with a central wavelength of 4.6 μm, indicating that optical with a wavelength of 4.6 μm can be used to generate stable oscillations using the mirrors (Fig.8). The total transmittance of the 1×2 MMI output port with the taper is 99.8%, and the optical field distribution is clear and stable, indicating that uniform beam splitting with low loss is achieved (Fig.9 and Fig.10). Due to the high symmetry of the beam splitter, each beam passes through waveguides of equal length, resulting in consistent phase at the amplification end. A comparison is made between different amplifier array spacings in terms of temperature and far-field distribution (Fig.11 and Fig.14). The output port of the array is coated with Al2O3 coating, and its high transmittance can further increase the output power of the laser (Fig.13).
      Conclusions  Aiming at the low output power of the current single QCL, a QCL phase-locked array with an operating wavelength of 4.6 μm is designed to improve the output power of the laser. The epitaxial thickness of each layer of the device is determined by mode analysis, combining the calculation of optical limiting factor and waveguide transmission loss, and the single-mode waveguide is designed. The waveguide loss is 0.055dB·cm-1, and the optical limiting factor is 0.733. A seed laser with a laser wavelength of 4.6 μm is designed by using a resonator composed of 100% and 50% Bragg mirrors. The 1×16 low loss splitter is designed by using MMI and bending waveguide, and its loss is 0.254 dB. The output port is plated with 0.7 μm thick Al2O3 anti-reflection coating, and the transmission rate can reach 0.975, which further improves the output power of the laser.

     

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